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Expression and presence of the platelet-activating factor receptor in human embryos

2003; Elsevier BV; Volume: 79; Issue: 5 Linguagem: Inglês

10.1016/s0015-0282(03)00073-6

1556-5653

William E. Roudebush, Joe B. Massey, Hilton I. Kort, Carlene W. Elsner, Andrew A. Toledo, Daniel B. Shapiro,

Pregnancy and preeclampsia studies

Platelet-activating factor [1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; PAF] is a unique signaling phospholipid that has pleiotropic biological properties in addition to platelet activation (1Hanahan D.J. Platelet-activating factor a biologically active phosphoglyceride.Annu Rev Biochem. 1986; 55: 483-509Crossref PubMed Google Scholar, 2Braquet P. Touqui L. Shen T.Y. Vargaftig B.B. Perspectives in platelet activating factor research.Pharmacol Rev. 1987; 39: 97-144PubMed Google Scholar). PAF is involved in a number of reproductive and developmental processes (3Harper M.J.K. Platelet activating factor a paracrine factor in preimplantation stages of development?.Biol Reprod. 1989; 40: 907-913Crossref PubMed Scopus (119) Google Scholar, 4Pike I.L. Ammit A.J. O’Neill C. Actions of platelet activating factor (PAF) on gametes and embryos clinical aspects.Reprod Fertil Dev. 1992; 4: 399-410Crossref PubMed Scopus (12) Google Scholar, 5Minhas B.S. Ripps B.A. Zhu Y.P. Kim H.N. Burwinkel T.H. Gleicher N. Platelet activating factor and conception.Am J Reprod Immunol. 1996; 35: 267-271Crossref PubMed Scopus (23) Google Scholar) including ovulation (6Kikukawa Y. Ishikawa M. Sengoku K. Kasama M. Shimizu T. The effect of platelet activating factor on ovulation.Prostaglandins. 1991; 42: 95-104Crossref PubMed Scopus (15) Google Scholar), fertilization (7Roudebush W.E. Minhas B.S. Ricker D.D. Palmer T.V. Dodson M.G. PAF enhances in vitro fertilization of rabbit oocytes.Am J Obstet Gynecol. 1990; 163: 1670-1673Abstract Full Text PDF PubMed Scopus (45) Google Scholar), preimplantation development (8Roberts C. O’Neill C. Wright L. Platelet-activating factor (PAF) enhances mitosis in preimplantation mouse embryos.Reprod Fertil Dev. 1993; 5: 271-279Crossref PubMed Scopus (45) Google Scholar), implantation(9Psychoyos A. Nikas G. Gravanis A. The role of prostaglandins in blastocyst implantation.Hum Reprod. 1995; 10: 30-42Crossref PubMed Scopus (85) Google Scholar), and parturition (10Silver R.K. Caplan M.S. Kelly A.M. Amniotic fluid platelet-activating factor is elevated in patients with tocolytic failure and preterm delivery.Prostaglandins. 1992; 43: 181-187Crossref PubMed Scopus (19) Google Scholar). Embryos produce PAF and this embryo-derived PAF can act as an autocrine stimulator of embryo development (11Ryan J.P. O’Neill C. Ammit A.J. Roberts C.G. Metabolic and developmental responses of preimplantation embryos to platelet activating factor.Reprod Fertil Dev. 1992; 4: 387-398Crossref PubMed Scopus (27) Google Scholar). PAF production by human embryos has been correlated with pregnancy potential (12O’Neill C. Gidley-Baird A.A. Ammit A.J. Saunders D.M. Use of a bioassay for embryo-derived PAF as a means of assessing quality and pregnancy potential of human embryos.Fertil Steril. 1987; 47: 969-975Abstract Full Text PDF PubMed Google Scholar, 13Roudebush W.E. Wininger J.D. Jones A. Wright G. Kort H.I. Massey J.B. Embryonic platelet-activating factor an indicator of embryo viability.Hum Reprod. 2002; 17: 1306-1310Crossref PubMed Scopus (36) Google Scholar). In other cell types, PAF’s action is receptor mediated, and it appears that PAF’s action in the embryo may be receptor mediated because different PAF-antagonists competitively inhibit its action (14Nishi O. Tominaga T. Gotot Y. Hayashi K. Mori T. Effects of platelet activating factor on mouse embryo implantation in vitro.J Assist Reprod Genet. 1995; 12: 330-334Crossref PubMed Scopus (14) Google Scholar). Only recently has the PAF receptor been characterized in the mouse (15Ishii S. Matsuda Y. Nakamura M. Waga I. Kume K. Izumi T. et al.A murine PAF receptor gene cloning, chromosomal localization and up-regulation of expression by lipopolysaccharide in peritoneal resident macrophages.Biochem J. 1996; 314: 671-678Crossref PubMed Scopus (50) Google Scholar, 16Roudebush W.E. LaMarche M.D. Levine A.S. Jiang H.H. Butler W.J. Evidence for the presence of the platelet-activating factor-receptor in the CFW mouse preimplantation two-cell stage embryo.Biol Reprod. 1997; 57: 575-579Crossref PubMed Scopus (31) Google Scholar). There are no reports on the expression or presence of the PAF receptor in the human embryo. Therefore, our study objective was to confirm or deny the expression and presence of the PAF receptor by the human preimplantation embryo. Fresh, human, day 3 (day 1 = pronuclear stage) embryos, produced by conventional in vitro fertilization (IVF) for clinical purposes, were donated by individuals after informed consent, and with institutional review board approval. Controlled ovarian hyperstimulation and in vitro fertilization were performed as previously described (13Roudebush W.E. Wininger J.D. Jones A. Wright G. Kort H.I. Massey J.B. Embryonic platelet-activating factor an indicator of embryo viability.Hum Reprod. 2002; 17: 1306-1310Crossref PubMed Scopus (36) Google Scholar). Day-3 morphologically normal embryos were cultured in modified minimum essential medium (alpha modification, Sigma Chemical Co., St. Louis, MO) to the blastocyst stage (16Roudebush W.E. LaMarche M.D. Levine A.S. Jiang H.H. Butler W.J. Evidence for the presence of the platelet-activating factor-receptor in the CFW mouse preimplantation two-cell stage embryo.Biol Reprod. 1997; 57: 575-579Crossref PubMed Scopus (31) Google Scholar). The expression of PAF-receptor mRNA was detected by reverse transcription-polymerase chain reaction (RT/PCR) and its presence was confirmed by immunofluorescence microscopy. RNA extraction, RT/PCR, DNA cloning, and sequencing were performed as previously described (16Roudebush W.E. LaMarche M.D. Levine A.S. Jiang H.H. Butler W.J. Evidence for the presence of the platelet-activating factor-receptor in the CFW mouse preimplantation two-cell stage embryo.Biol Reprod. 1997; 57: 575-579Crossref PubMed Scopus (31) Google Scholar). Immunofluorescence microscopy was performed as follows. Zona pellucidae were removed from fresh human blastocysts by acid Tyrode’s (pH 2.5). The zona-free blastocysts were washed in phosphate-buffered saline and exposed to rabbit PAF receptor or rabbit preserum (control) antibody at 4°C. Following a 60-minute treatment period, the blastocysts were washed in phosphate-buffered saline then exposed to fluorescein isothiocyanate-conjugated antirabbit IgG (Sigma Chemical Co.) for 10 minutes at 4°C, and again washed in phosphate-buffered saline. Immunofluorescent microscopy was performed using a Zeiss Axioplan microscope (Carl Zeiss, Thornwood, NY) equipped with an epifluoresence filter. The presence of PAF receptors on the human embryo was confirmed by immunofluorescene (Fig. 1A). A cDNA clone containing the coding region for human PAF receptor was isolated from human blastocysts using a RT/PCR protocol (Fig. 1B). The cDNA sequence (GenBank Accession No. XM_038986) was found to be 99% homologous to other human cDNA sequences (e.g., GenBan Accession Nos. XM_038986.4 and M80436). However, the deduced protein sequence differed from known human sequences (e.g., GenBank Accession Nos. NM_000952 and S52624) by 47 amino acids (76% homology). In this study we demonstrated the expression (mRNA) and presence (protein) of the PAF receptor in a human preimplantation embryo. Preimplantation-stage embryos in a variety of species (human, mouse, sheep, and rabbit) produce and release PAF (17O’Neill C. Partial characterization of the embryo-derived platelet-activating factor in mice.J Reprod Fertil. 1985; 75: 375-380Crossref PubMed Scopus (123) Google Scholar, 18Collier M. O’Neill C. Ammitt A.J. Saunders D.M. Biochemical and pharmacological characterization of human embryo-derived activating factor.Hum Reprod. 1988; 3: 993-998PubMed Google Scholar, 19Battye K.M. Ammitt A.J. O’Neill C. Evans G. Production of platelet-activating factor by the preimplantation sheep embryo.J Reprod Fertil. 1991; 93: 507-514Crossref PubMed Scopus (39) Google Scholar). PAF production by human preimplantation embryos is related to their subsequent pregnancy potential (12O’Neill C. Gidley-Baird A.A. Ammit A.J. Saunders D.M. Use of a bioassay for embryo-derived PAF as a means of assessing quality and pregnancy potential of human embryos.Fertil Steril. 1987; 47: 969-975Abstract Full Text PDF PubMed Google Scholar, 13Roudebush W.E. Wininger J.D. Jones A. Wright G. Kort H.I. Massey J.B. Embryonic platelet-activating factor an indicator of embryo viability.Hum Reprod. 2002; 17: 1306-1310Crossref PubMed Scopus (36) Google Scholar). Furthermore, mouse preimplantation embryos cultured in the presence of PAF have enhanced development (20Ryan J.P. Spinks N.R. O’Neill C. Ammit A.J. Wales R.G. Platelet activating factor (PAF) production by mouse embryos in vitro and its effect on embryonic metabolism.J Cell Biochem. 1999; 40: 387-395Crossref Scopus (55) Google Scholar) and higher implantation rates upon transfer to synchronized recipients (21Nishi O. Tominaga T. Goto Y. Hayashi K. Mori T. Effects of platelet activating factor on mouse embryo implantation in vitro.J Assist Reprod Genet. 1995; 12: 330-334Crossref PubMed Scopus (15) Google Scholar). PAF directly influences the oxidative metabolism of glucose and lactate in the mouse preimplantation embryo (22Ryan J.P. O’Neill C. Wales R.G. Platelet-activating factor directly influences the oxidative metabolism of glucose and lactate in the preimplantation mouse embryo.J Reprod Fertil. 1990; 89: 301-307Crossref PubMed Scopus (54) Google Scholar). PAF antibodies inhibit embryo development (23Roudebush W.E. Mathur S. Butler W.J. Anti-PAF antibody inhibits CFW mouse preimplantation embryo development.J Assist Reprod Genet. 1994; 11: 1-5Crossref PubMed Scopus (4) Google Scholar) and antagonists inhibit implantation (24Andu M. Suginami H. Matsuura S. Pregnancy suppression by a structurally related antagonist for platelet-activating factor.Asia Oceania J Obstet Gynecol. 1990; 16: 283-290Crossref PubMed Scopus (13) Google Scholar), providing further evidence, albeit indirect, of the presence of and requirement for embryo-derived PAF during the preimplantation and peri-implantation periods. PAF receptors, expressed by the transformed endometrial cell line HEC-1B, are functionally linked to inositol lipid hydrolysis, the mobilization of intracellular-free calcium, and activation of a tyrosine kinase pathway (25Ahmed A. Sage S.O. Plevin R. Shoaibi M.A. Sharkey A.M. Smith S.K. Functional platelet-activating factor receptors linked to inositol lipid hydrolysis, calcium mobilization and tyrosine kinase activity in the human endometrial HEC-1B cell line.J Reprod Fertil. 1994; 101: 459-466Crossref PubMed Scopus (26) Google Scholar). Although it has yet to be reported in preimplantation-stage embryos, PAF binds to cell surface receptors, causing the formation of inositol triphosphate (IP3) and diacylglycerol (DAG) (26Lapetina E.G. PAF stimulates the phosphatidylinositol cycle.J Biol Chem. 1982; 257: 7314-7317Abstract Full Text PDF PubMed Google Scholar). Exogenous PAF has been demonstrated to affect intracellular calcium levels in mouse preimplantation two-cell stage embryos (16Roudebush W.E. LaMarche M.D. Levine A.S. Jiang H.H. Butler W.J. Evidence for the presence of the platelet-activating factor-receptor in the CFW mouse preimplantation two-cell stage embryo.Biol Reprod. 1997; 57: 575-579Crossref PubMed Scopus (31) Google Scholar, 27Stachecki J.J. Yelian F.D. Schultz J.F. Leach R.E. Armant D.R. Mouse blastocyst outgrowth and implantation rates following exposure to ethanol or A23187 during culture in vitro.Biol Reprod. 1994; 50: 1-7Crossref PubMed Scopus (54) Google Scholar). Blastocyst cavitation and fluid accumulation can be accelerated by an increase in intracellular calcium induced by ethanol or ionophore-A23187 (28Hanson P.I. Meyer T. Stryer L. Schulman H. Dual role of calmodulin in autophosphorylation of multifunctional CaM kinase may underlie decoding of calcium signals.Neuron. 1994; 12: 943-956Abstract Full Text PDF PubMed Scopus (382) Google Scholar). PAF may bind to cell surface receptors on preimplantation embryos, initiating the formation of IP3 and DAG, and increasing intracellular calcium. As a secondary messenger, calcium may regulate preimplantation embryonic development by modulating the activity of molecules that transduce intracellular signals, which in turn influences embryonic growth and development. In summary, we have demonstrated the expression (mRNA) and presence (protein) of the PAF receptor in the human preimplantation embryo. Human preimplantation embryos produce PAF and its receptor; the PAF ligand specifically binds to its receptor, which can be blocked by PAF antibodies or antagonists, resulting in increased intracellular calcium levels, increased mitotic rates, and enhanced growth, development, and implantation. The collective data provide further evidence that PAF’s effect on preimplantation embryo development is receptor mediated and may involve the inositol triphosphate system. PAF may affect preimplantation embryonic development by regulation of intracellular calcium levels. The data provide a clue to the complicated signal-transduction system following embryonic PAF synthesis and PAF-receptor expression and may help our understanding of the communication between preimplantation embryos and endometrium required for implantation and pregnancy.